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Re: I'm doing something wrong with map_image [message #76374 is a reply to message #76373]

Tue, 31 May 2011 18:05

almost_like_a_metapho is currently offline

almost_like_a_metapho
Messages: 8
Registered: May 2011

Junior Member

On May 31, 6:05 pm, David Fanning <n...@idlcoyote.com> wrote:

> Here is an example. Suppose this image is map projected
> (I'm not sure it is):
>
> cgloadct, 0
> image = congrid(shift(cgDemoData(7), 180, 0), 3000, 1500)
> cgimage, image, /keep, position=p
> map_set, /noerase, position=p
> map_grid
> map_continents
> plots, [20, 20, 0, 0, 20], [20, 0, 0, 20, 20], color=cgcolor('blue')
> plots, 10, 10, psym=4, color=cgcolor('yellow')
>
> Cheers,
>
> David
>

OK, from your example, what I want to display is a window that zooms
in on just that blue box - where the coordinates of the box bound the
window. Since I'm using simple cylindrical projection, I thought I
could get away with just putting the image as a background to a plot
window, as long as the axes and image corners aligned. I think my
issue is that I was insisting on thinking of it as a data plot with an
image background, and I really need to think of it as a displayed map
image with shapes overplotted.

So, if my base image is a global map, and all I want to do is take one
3x3 degree piece of it, display that, and plot my grid lines and data-
overlay on it, do I have to create a small, subsampled "image" from
your example above? Or can I simply display a smaller part of the
image? in cgimage, image[lonrange,latrange]? Though in that case I
think I'll have to convert my lat/lon ranges to image coordinates.

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[Message index]

		Re: I'm doing something wrong with map_image By: almost_like_a_metapho on Tue, 31 May 2011 21:22
		Re: I'm doing something wrong with map_image By: David Fanning on Tue, 31 May 2011 20:48
		Re: I'm doing something wrong with map_image By: almost_like_a_metapho on Tue, 31 May 2011 18:05
		Re: I'm doing something wrong with map_image By: David Fanning on Tue, 31 May 2011 15:05
		Re: I'm doing something wrong with map_image By: David Fanning on Tue, 31 May 2011 14:41
		Re: I'm doing something wrong with map_image By: David Fanning on Tue, 31 May 2011 14:33
		Re: I'm doing something wrong with map_image By: almost_like_a_metapho on Tue, 31 May 2011 14:31
		Re: I'm doing something wrong with map_image By: David Fanning on Tue, 31 May 2011 14:10
		Re: I'm doing something wrong with map_image By: almost_like_a_metapho on Wed, 01 June 2011 16:32

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